Fuzz testing (fuzzing) is a powerful technique for generating large numbers of diverse inputs - either randomly or algorithmically - and dynamically invoking the code with those inputs. Even with random inputs, it is often capable of generating unexpected results such as crashes, memory corruption, or resource consumption. Fuzzing effectively produces repeatable test cases that clearly indicate bugs, which helps developers to diagnose the issues.
CWE-590 Variante Incompleto
Free of Memory not on the Heap
This vulnerability occurs when a program calls free() on a memory pointer that wasn't originally allocated using standard heap functions like malloc(), calloc(), or realloc().
Definición
What is CWE-590?
This vulnerability occurs when a program calls free() on a memory pointer that wasn't originally allocated using standard heap functions like malloc(), calloc(), or realloc().
Calling free() on an invalid pointer corrupts the program's internal memory management structures. This corruption typically leads to a crash, but it can also create opportunities for an attacker to manipulate the memory process. In some cases, an attacker can steer the free() operation to target controllable memory locations, potentially altering critical variables or even executing malicious code.
Detecting these 'invalid free' issues manually is challenging, as they often involve complex pointer tracking across codebases. While SAST tools can flag the pattern, Plexicus uses AI to analyze the data flow and suggest precise code fixes, transforming a tedious security hunt into an automated remediation step and saving significant developer time.
Impacto en el mundo real
Real-world CVEs caused by CWE-590
Todavía no hay CVEs públicos enlazados a esta CWE en el catálogo de MITRE.
Cómo lo explotan los atacantes
Ruta del atacante paso a paso
- 1
In this example, an array of record_t structs, bar, is allocated automatically on the stack as a local variable and the programmer attempts to call free() on the array. The consequences will vary based on the implementation of free(), but it will not succeed in deallocating the memory.
- 2
This example shows the array allocated globally, as part of the data segment of memory and the programmer attempts to call free() on the array.
- 3
Instead, if the programmer wanted to dynamically manage the memory, malloc() or calloc() should have been used.
- 4
Additionally, global variables could be passed to free() when they are pointers to dynamically allocated memory.
Ejemplo de código vulnerable
Vulnerable C
In this example, an array of record_t structs, bar, is allocated automatically on the stack as a local variable and the programmer attempts to call free() on the array. The consequences will vary based on the implementation of free(), but it will not succeed in deallocating the memory.
void foo(){
record_t bar[MAX_SIZE];
```
/* do something interesting with bar */*
...
free(bar);} Ejemplo de código seguro
Secure C
Instead, if the programmer wanted to dynamically manage the memory, malloc() or calloc() should have been used.
void foo(){
record_t *bar = (record_t*)malloc(MAX_SIZE*sizeof(record_t));
```
/* do something interesting with bar */*
...
free(bar);} What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Lista de prevención
How to prevent CWE-590
- Implementation Only free pointers that you have called malloc on previously. This is the recommended solution. Keep track of which pointers point at the beginning of valid chunks and free them only once.
- Implementation Before freeing a pointer, the programmer should make sure that the pointer was previously allocated on the heap and that the memory belongs to the programmer. Freeing an unallocated pointer will cause undefined behavior in the program.
- Architecture and Design Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, glibc in Linux provides protection against free of invalid pointers.
- Architecture and Design Use a language that provides abstractions for memory allocation and deallocation.
- Testing Use a tool that dynamically detects memory management problems, such as valgrind.
Señales de detección
How to detect CWE-590
Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)
CWE-590
Don't catalog this weakness. Prove it's reachable.
Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.
Preguntas frecuentes ¿Qué es CWE-590?
¿Qué gravedad tiene CWE-590?
¿Qué lenguajes o plataformas se ven afectados por CWE-590?
¿Cómo puedo prevenir CWE-590?
¿Cómo detecta y corrige Plexicus CWE-590?
¿Dónde puedo aprender más sobre CWE-590?
Frequently asked questions
¿Qué es CWE-590?
This vulnerability occurs when a program calls free() on a memory pointer that wasn't originally allocated using standard heap functions like malloc(), calloc(), or realloc().
¿Qué gravedad tiene CWE-590?
MITRE no ha publicado una calificación de probabilidad de explotación para esta debilidad. Trátala como de impacto medio hasta que tu modelo de amenazas demuestre lo contrario.
¿Qué lenguajes o plataformas se ven afectados por CWE-590?
MITRE no ha especificado plataformas afectadas para esta CWE — puede aplicar a la mayoría de los stacks de aplicaciones.
¿Cómo puedo prevenir CWE-590?
Only free pointers that you have called malloc on previously. This is the recommended solution. Keep track of which pointers point at the beginning of valid chunks and free them only once. Before freeing a pointer, the programmer should make sure that the pointer was previously allocated on the heap and that the memory belongs to the programmer. Freeing an unallocated pointer will cause undefined behavior in the program.
¿Cómo detecta y corrige Plexicus CWE-590?
El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-590 en cada commit. Cuando hay coincidencia, nuestro agente Codex Remedium abre un PR de corrección con el código corregido, las pruebas y un resumen de una línea para el revisor.
¿Dónde puedo aprender más sobre CWE-590?
MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/590.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.
Debilidades relacionadas
Weaknesses related to CWE-590
CWE-762 Padre
Mismatched Memory Management Routines
This vulnerability occurs when a program uses incompatible functions to allocate and free memory. For example, freeing memory with a…
CWE-123 Puede preceder
Write-what-where Condition
A write-what-where condition occurs when an attacker can control both the data written and the exact memory location where it's written,…
Recursos
Further reading
¿Listo para validar lo que importa?
Listo para validar lo que importa.
Plexicus es Proof-Driven AppSec: hallazgos validados, comprensión contextual y remediación revisada — anclada en evidencia, acotada contigo.